Evolution of multi-fungicide resistance in cereal pathogens and impact on disease controlBart Fraaije: Rothamsted Research

<div>NW-Europe is always under high disease pressure of fungal pathogens due to favourable weather conditions and a high intensity of cereal production. Host resistance breeding has provided good control of powdery mildews and rusts, albeit subjected to boom-and-bust cycles of major single resistance genes, but it has proved more difficult to control diseases such as Septoria, net blotch and Ramularia. Control of these diseases has been heavily dependent on chemical control. Unfortunately, pathogens like <i>Zymoseptoria tritici</i>, <i>Pyrenophora teres</i> and <i>Ramularia collo-cygni</i> have been able to shown a remarkable adaptation to fungicides over the years and current UK field populations are resistant or less sensitive to different groups of systemic fungicides, including benzimidazoles, quinone outside inhibitors and azoles. As a consequence, farmers have only a few options available to control these diseases. Further threats for disease control are the first reports of resistance development to the most effective group of fungicides, the succinate dehydrogenase inhibitors (SDHIs), in different pathogen field populations, and loss of current actives and drying up of the fungicide pipeline due to tighter legislation. DNA diagnostics able to measure the dynamics of SDHI-resistant alleles in <i>Z. tritici</i>populations are now being used to establish which strategies are most effective for resistance management and can help to extend the shelf life of current and future fungicides.</div>